TITLE: GCN CIRCULAR NUMBER: 44498 SUBJECT: EP260507a: COLIBRÍ optical observations DATE: 26/05/08 06:07:02 GMT FROM: globus@astro.unam.mx Noémie Globus (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260507a (Fu et al., GCN Circ. 44488) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-08 04:59 to 05:50 UTC (from 15.19 to 16.06 hours after the trigger) and obtained 39 minutes of exposure in the r and z filters, respectively. The data were reduced and coadded with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the optical candidate reported previously (Corcoran et al., GCN Circ. 44489; Sankar et al., GCN Circ. 44490; Jiang et al., GCN Circ. 44491; Kumar et al., GCN Circ. 44492; Bochenek et al., GCN Circ. 44494; Eyles-Ferris et al., GCN Circ. 44495; Jiang et al., GCN Circ. 44496) with preliminary magnitudes of: r = 23.37 +/- 0.14, z = 22.44 +/- 0.21. From a combined power-law fit including our data and previously reported GCN Circular measurements, we derive a temporal decay index of α ≈ 0.6. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/44498. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...